ERBB2 and metastatic neoplasm: Cox proportional hazard regression analysis of PFS according to SNAI2 level and clinicopathological characteristics of the metastatic disease, including age, site of relapse and HER2 status (Table 2), showed that SNAI2 was independently prognostic of PFS on endocrine therapy in both cohorts (cohort 1, HR 2.11, 95% CI of the ratio, 1.21–3.66, p = 0.008; cohort 2, HR 1.92, 95% CI of the ratio, 1.03–3.59, p = 0.04).